Comparison of fungal culture versus surgical pathology examination in the detection of Histoplasma in surgically excised pulmonary granulomas.

CONTEXT: Granulomatous pulmonary nodules are common in areas endemic for Histoplasma infection, and may require surgical excision to exclude neoplasia. Surgeons may elect to routinely send material directly to the clinical microbiology laboratory for fungal and mycobacterial cultures. OBJECTIVE: To determine if tissue from surgically excised pulmonary granulomatous nodules removed from patients in a geographic area endemic for Histoplasma infection should be routinely submitted for fungal culture. DESIGN: Retrospective review and comparison of surgical pathology histochemical findings and clinical microbiology results of 30 surgical (wedge) lung excisions that demonstrated granulomatous nodule at the time of frozen section. RESULTS: Twenty cases demonstrated fungal organisms consistent with Histoplasma species via histochemical fungal stains. Of these 20 cases, 17 were tested in the microbiology laboratory using direct smear examination and fungal culture; Histoplasma was detected in 1 case (1/17). Eight cases revealed no organisms by surgical pathology. Of these, 6 were tested in the microbiology laboratory, and all 6 were negative by culture and direct smear (0/6). The remaining 2 cases demonstrated organisms other than Histoplasma by surgical pathology examination. CONCLUSIONS: Surgical pathology examination of granulomatous pulmonary nodules detected Histoplasma organisms with greater sensitivity than culture and direct smear. There were no false-negative surgical pathology diagnoses when compared with microbiological results. These findings suggest that it is not necessary to routinely send material from solitary pulmonary granulomas for fungal culture when the material is removed from immunocompetent patients in a geographic area endemic for histoplasmosis.